This invention relates to a sensor. More particularly, the invention relates to an inexpensive disposable sensor that can be used to sense forces exerted by the human body during such movements as walking, jogging and in orthopedic testing.
In recent years studies of human gait by orthopedic testing involve the accumulation of quantitative measurements of the forces exerted by the foot against the ground. Such information has proven particularly effective in diagnosing and treating neurological and muscular abnormalities. Such studies are described in, for example, U.S. Pat. No. 2,290,387. Studies of the human gait have also been found useful in the diagnosis and treatment of orthopedic foot disorders. An example of such a study is described in L. F. Dragnich et al, Measurement of Instantaneous Foot--Floor Contact Patterns, Orthopedic Research Society, Orthopedic Transactions 1980, Vol. 4 #2 at p. 242.
Recently, human gait studies have been used for both diagnosis and treatment in sports medicine and biomechanics. These studies are used analytically to measure the force and movement generated by an athlete's foot during training and competition. Based on such measurements, special training exercises and techniques have been devised to improve the athlete's competitive performance.
A number of different types of measuring devices are employed to measure the forces exerted by a subject during movements, as in walking, running or the like. For example, U.S. Pat. No. 2,095,268 describes an orthopedic pressure sensing device which employs a fluid-containing diaphragm. As a subject stands and walks on the device, the pressure applied to the diaphragm is measured. Similar fluid-containing diaphragms are also described in two U.S. Pat. Nos. 2,192,435 and 3,974,491.
Electrical means for measuring human gait is taught in the above-mentioned U.S. Pat. No. 2,290,387. Piezoelectric mutlicomponent measuring platforms have been marketed for a number of years. For example, a quartz multicomponent measuring platform is marketed by Kistler Instruments A.G. of Wintertherm, Switzerland. More recently, multiaxial load cells employing small foil type strain gauges have been incorporated in a subject's shoe to measure gait. See, for example. H. S. Ranu et al, A Study of Normal and Abnormal Human Gait With Miniature Triaxial Shoe-Borne Load Cells, Orthopedic Research Society, Orthopedic Transactions 1980, Vol. 4 #2 at p. 240.
These prior art devices for measuring gait all have numerous disadvantages. For example, fluid filled diaphragm devices have proven inaccurate. Further, it has been found that devices which utilize either a platform or pad on which a subject stands, or a specially fitted shoe which must be worn by a subject, are cumbersome and difficult to use. Rigid or bulky sensors mounted in shoes or on the body are uncomfortable and this discomfort has been known to affect the validity of the test since it may affect a subject's movements or gait. Moreover, when the sensor is placed in a shoe, the shoe is specially modified to accommodate the sensor such that the shoe must be discarded after such special use.
It is therefore an object of the present invention to provide a durable force sensor of thin, planar, flexible construction.
It is another object of the present invention to provide a thin, flexible sensor for use in measuring the forces exerted by the human body which is comprised of two parts, one part being a permanent electrode and the other part being a conductive sensor pad adapted to be attached to the skin at a given test site and which is inexpensive so it can be discarded after use.
It is a further object of the present invention to provide a thin, flexible force sensor for use on the human body wherein the sensor is comprised of two parts detachably joined together so that that part of the sensor which is in immediate contact with the body can be discarded after use thereby to facilitate sanitary test procedures.
It is another object of the present invention to provide a pressure transducer adapted to measure forces exerted by the human body wherein the transducer is of minimal thickness, employs a change in electric resistance as a parameter corresponding to the applied force, and which is low in cost.